People are developing dementia a decade before they were 20 years ago, perhaps because of environmental factors such as pollution and the stepped-up use of insecticides, a wide-ranging international study has found.

The study, which compared 21 Western countries between the years 1989 and 2010, found that the disease is now being regularly diagnosed in people in their late 40s and that death rates are soaring.

The study was published in the Surgical Neurology International journal, and its findings publicized in the London Times newspaper Thursday.

The problem was particularly acute in the United States, where neurological deaths in men aged over 75 have nearly tripled and in women risen more than fivefold, the leader of the study, Colin Pritchard from Bournemouth University, told the London Times.

Scientists quoted in the study said a combination of environmental factors such as pollution from aircraft and cars as well as widespread use of pesticides could be the culprit, the newspaper reported.

Early-onset dementia used to cover people developing the disease in their late 60s. Now, it’s meant to mean people much younger than that, the research showed.

The study found that deaths caused by neurological disease had risen significantly in adults aged 55 to74, virtually doubling in the over-75s.

Some 60 percent of the increase in deaths was attributed to dementias. Some 40 percent covered other neurological diseases such as Parkinson's and motor neurone disease, scientists told the London newspaper.

The sharp increase in death rates from dementia-related diseases cannot simply be blamed on an aging population or stepped-up diagnosis, Pritchard said.

“The rate of increase in such a short time suggested a silent or even a hidden epidemic, in which environmental factors must play a major part, not just aging,” he was quoted as saying. Pritchard said no single factor was to blame, but instead blamed the interaction between different chemicals and varying ypes of pollution.

“The environmental changes in the last 20 years have seen increases in the human environment of petro-chemicals — air transport, quadrupling of motor vehicles, insecticides and rises in background electro-magnetic field, and so on,” Pritchard was quoted by the newspaper as saying. The scientists said nobody wanted to put an end to modern advances. Instead, to make them safer.

Other experts quoted by the newspaper were skeptical about the causes for the increase.

Tom Dening, professor of dementia research at the University of Nottingham, said that falling death rates for cancer and heart disease could account for the spike in deaths from neurological disease since people “had to die of something.”

“We can’t conclude that modern life is causing these conditions at a younger age,” Dr. Simon Ridley, head of research at Alzheimer’s Reserach UK told the paper. “We know that Alzheimer’s and other dementias can have a complex interplay of risk factors.”

Pritchard warned, however, that it was “time for us to wake up and realise that a major problem we now face is unprecedented levels of neurological disease, not just the early dementias.”

Deane reported from Rome.

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